Pixel structure having high aperture ratio and circuit

ABSTRACT

The present invention provides a pixel structure having high aperture ratio and circuit. The first gate ( 21 ), the first source/the first drain ( 61 ), and the etching stopper layer ( 5 ), the first semiconductor layer ( 41 ), the gate isolation layer ( 3 ) sandwiched in-between of the pixel structure having high aperture ratio construct a first thin film transistor (TFT 1 ); the second gate ( 22 ), the second source/the second drain ( 62 ), and the etching stopper layer ( 5 ), the second semiconductor layer ( 42 ), the gate isolation layer ( 3 ) sandwiched in between construct a second thin film transistor (TFT 2 ); the transparent electrode ( 8 ), the pixel electrode ( 10 ) and the flat isolation layer ( 9 )sandwiched in-between construct a transparent capacitor (C), and the transparent capacitor (C) constructs an activation area part of the pixel structure which is capable of increasing the activation area of the pixel and raising the aperture ratio to increase the display brightness and reduce the power consumption.

FIELD OF THE INVENTION

The present invention relates to a display technology field, and moreparticularly to a pixel structure having high aperture ratio and acircuit.

BACKGROUND OF THE INVENTION

A flat panel display possesses advantages of being ultra thin, powersaved and radiation free and has been widely utilized. Present flatpanel displays mainly comprise a LCD (Liquid Crystal Display) or an OLED(Organic Light Emitting Display).

An Organic Light Emitting Diodes Display possesses outstandingproperties of self-illumination, no required back light, high contrast,being ultra thin, wide view angle, fast response, being applicable forflexible panel, wide usage temperature range, simple structure andmanufacture process and etc., therefore, it is considered to be a newapplicable technology for the next generation flat panel display.

The OLEDs can be categorized as PM-OLED (Passive matrix OLED) andAM-OLED (Active matrix OLED). The AM-OLED panels belong to activedisplay type, and require manufacturing pixel structures in array on thearray substrate. As shown in FIG. 1, generally in each of the pixelstructures in the present AM-OLED, two Thin Film Transistors (TFT)sandwich a storage capacitor in-between. Specifically, the first thinfilm transistor TFT1′ comprises a first gate 210, a first source/a firstdrain 610 and an etching stopper layer 500, a first semiconductor layer410, a gate isolation layer 300 sandwiched in-between; the second thinfilm transistor TFT2′ comprises a second gate 220, a second source/asecond drain 620 and an etching stopper layer 500, a secondsemiconductor layer 420, a gate isolation layer 300 sandwichedin-between; the storage capacitor C′ comprises a first metal electrode230 formed by the first, the second gates 210, 220, and a second metalelectrode 630 formed by the first source/the first drain, the secondsource/the second drain 610, 620, and the etching stopper layer 500 andthe gate isolation layer 300 sandwiched between the two electrodes.Because the metal material shields the light and blocks the penetrationof the light, the first, the second thin film transistors TFT1′, TFT2′and the storage capacitor C′ must occupy a certain area of the pixel,which leads to reduce the activation area of the pixel, i.e. to reducethe aperture ratio. It enormously restricts the usage ratio of thelight. Particularly as for the high resolution, bottom emitting AM-OLED,the decrease of the aperture ratio gets even worse, which easily causesproblems of the insufficient brightness and over large powerconsumption.

FIG. 2 is an equivalent circuit diagram of FIG. 1. The first thin filmtransistor TFT1′ is employed as single switch thin film transistor. Thesecond thin film transistor TFT2′ is employed as a drive thin filmtransistor. Specifically, a gate of the first thin film transistor TFT1′is coupled to a gate drive voltage signal V_(gate), and a source thereofis coupled to a data drive voltage signal V_(data), and a drain thereofis coupled to a gate of the second thin film transistor TFT2′; a sourceof the second thin film transistor TFT2′ is coupled to a drive voltagesignal V_(dd), and a drain thereof is coupled to an anode of the organiclight emitting diode D; a cathode of the organic light emitting diode Dis coupled to a ground signal V_(ss); one electrode of the transparentcapacitor C′ is coupled to the gate of the second thin film transistorTFT2′, and the other electrode thereof is coupled to the source of thesecond thin film transistor TFT2′.

The working principle of the circuit is: when the gate drive voltagesignal V_(gate) is present, the first thin film transistor TFT1′ isconducted, and the data drive voltage signal V_(data) is inputted to thegate of the second thin film transistor TFT2′ and the second thin filmtransistor TFT2′ is conducted. The drive voltage signal V_(dd), drivethe organic light emitting diode D to display after being amplified bythe second thin film transistor TFT2′. When the gate drive voltagesignal V_(gate) disappears, the transparent capacitor C′ is a majormeans to maintain the voltage level of the pixel electrode.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a pixel structurehaving high aperture ratio, capable of increasing the activation area ofthe pixel and raising the aperture ratio to increase the displaybrightness and reduce the power consumption.

Another objective of the present invention is to provide a circuit of apixel structure having high aperture ratio, beneficial to raise theaperture ratio and promote the display effect.

For realizing the aforesaid objective, the present invention firstprovides a pixel structure having high aperture ratio, comprising asubstrate, a first gate and a second gate, located at one side of thesubstrate; a gate isolation layer, located on the first, the secondgates and the gate isolation layer, and the gate isolation layercompletely covers the first gate and the substrate, and exposes two endsof the second gate; a first semiconductor layer, located on the gateisolation layer and right over the first gate; a second semiconductorlayer, located on the gate isolation layer and right over the secondgate; an etching stopper layer, located on the first, the secondsemiconductor layer and the gate isolation layer; a first source/a firstdrain, located on the first semiconductor layer and the etching stopperlayer; a second source/a second drain, located on the secondsemiconductor layer and the etching stopper layer, and the firstsource/the first drain are connected to the first semiconductor layerand one end of the second gate, and the second source/the second drainare connected to the second semiconductor layer; a protective layer,located on the first source/the first drain, the second source/thesecond drain and the etching stopper layer; a transparent electrode,located on the protective layer and at the other side of the substrate,and the transparent electrode is connected to the other end of thesecond gate; a flat isolation layer, located on the protective layer andthe transparent electrode; a pixel electrode, located on the flatisolation layer, and the pixel electrode is connected to the secondsource/the second drain and overlaps with the transparent electrode; apixel definition layer, located on the flat isolation layer and thepixel electrode, and the pixel definition layer comprises an opencorresponding to an overlapping district of the pixel electrode and thetransparent electrode; the first gate, the first source/the first drain,and the etching stopper layer, the first semiconductor layer, the gateisolation layer sandwiched in-between construct a first thin filmtransistor; the second gate, the second source/the second drain, and theetching stopper layer, the second semiconductor layer, the gateisolation layer sandwiched in between construct a second thin filmtransistor; the transparent electrode, the pixel electrode and the flatisolation layer sandwiched in-between construct a transparent capacitor.

The transparent capacitor constructs an activation area part of thepixel structure.

The transparent electrode is an ITO transparent electrode or an IZOtransparent electrode, and the pixel electrode is an ITO pixel electrodeor an IZO pixel electrode.

The pixel structure having high aperture ratio further comprises aphotoresist spacer located on the pixel definition layer.

The pixel structure having high aperture ratio further comprises a firsttop gate electrode right over the first gate and between the protectivelayer and the flat isolation layer, and a second top gate electroderight over the second gate and between the protective layer and the flatisolation layer.

The first, the second top gate electrodes and the transparent electrodeare formed at the same time.

The first semiconductor layer is an IGZO semiconductor layer, and thesecond semiconductor layer is an IGZO semiconductor layer.

The present invention further provides a circuit of a pixel structurehaving high aperture ratio, comprising a first thin film transistor, asecond thin film transistor, a transparent capacitor, and a lightemitting diode, and both two electrodes constructing the transparentcapacitor are transparent electrodes; a gate of the first thin filmtransistor is coupled to a gate drive voltage signal, and a sourcethereof is coupled to a data drive voltage signal, and a drain thereofand a gate of the second thin film transistor are coupled; a source ofthe second thin film transistor is coupled to a drive voltage signal,and a drain thereof is coupled to an anode of the organic light emittingdiode; a cathode of the organic light emitting diode is coupled to aground signal; one electrode of the transparent capacitor is coupled tothe gate of the second thin film transistor, and the other electrodethereof is coupled to the source or the drain of the second thin filmtransistor.

The circuit of the pixel structure having high aperture ratio furthercomprises an opaque capacitor, and one electrode of the opaque capacitoris coupled to the gate of the second thin film transistor, and the otherelectrode thereof is coupled to the source or the drain of the secondthin film transistor.

The source, the drain of the first thin film transistor are switchable,and the source, the drain of the second thin film transistor are alsoswitchable.

The benefits of the present invention are: according to the pixelstructure having high aperture ratio of the present invention, byarranging the transparent capacitor constructed by the transparentelectrode and the pixel electrode, and the transparent capacitor isemployed as the activation area part for increasing the activation areaof the pixel and raising the aperture ratio to increase the displaybrightness and reduce the power consumption. According to the circuit ofthe pixel structure having high aperture ratio provided by the presentinvention, the aperture ratio can be raised and the display effect canbe promoted by arranging the transparent capacitor.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution, as well as beneficial advantages, of the presentinvention will be apparent from the following detailed description of anembodiment of the present invention, with reference to the attacheddrawings.

In drawings,

FIG. 1 is a sectional diagram of a pixel structure according to priorart;

FIG. 2 is an equivalent circuit diagram of the pixel structure shown inFIG. 1;

FIG. 3 is a sectional diagram of a pixel structure having high apertureratio according to the first embodiment of the present invention;

FIG. 4 is a sectional diagram of a pixel structure having high apertureratio according to the second embodiment of the present invention;

FIG. 5 is a schematic diagram of a circuit of a pixel structure havinghigh aperture ratio according to the first embodiment of the presentinvention;

FIG. 6 is a schematic diagram of a circuit of a pixel structure havinghigh aperture ratio according to the second embodiment of the presentinvention;

FIG. 7 is a schematic diagram of a circuit of a pixel structure havinghigh aperture ratio according to the third embodiment of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In order to better understand the characteristics and technical aspectof the invention, please refer to the following detailed description ofthe present invention is concerned with the diagrams.

The present invention first provides a pixel structure having highaperture ratio and FIG. 3 shows the first embodiment thereof. The pixelstructure having high aperture ratio comprises a substrate 1, and thesubstrate 1 can be a glass substrate or a plastic substrate;

-   -   a first gate 21 and a second gate 22, located at one side of the        substrate 1 and on the substrate 1, and the first gate 21 and        the second gate 22 are formed with the same first metal film        layer which has been patterned;    -   a gate isolation layer 3 located on the first, the second gates        21, 22 and the gate isolation layer 3 completely covers the        first gate 21 and the substrate 1, and exposes two ends of the        second gate 22;    -   a first semiconductor layer 41, located on the gate isolation        layer 3 and right over the first gate 21; a second semiconductor        layer 42, located on the gate isolation layer 3 and right over        the second gate 22; the first semiconductor layer 41 and the        second semiconductor layer 42 are formed with the same        semiconductor layer which has been patterned;    -   an etching stopper layer 5, located on the first, the second        semiconductor layer 41, 42 and the gate isolation layer 3;    -   a first source/a first drain 61, located on the first        semiconductor layer 41 and the etching stopper layer 5; a second        source/a second drain 62, located on the second semiconductor        layer 42 and the etching stopper layer 5; the first source/the        first drain 61 and the second source/the second drain 62 are        formed with the same second metal film layer which has been        patterned; the first source/the first drain 61 are connected to        the first semiconductor layer 41 and one end of the second gate        22, and the second source/the second drain 62 are connected to        the second semiconductor layer 42;    -   a protective layer 7, located on the first source/the first        drain, the second source/the second drain 61, 62 and the etching        stopper layer 5;    -   a transparent electrode 8, located on the protective layer 7 and        at the other side of the substrate 1, and the transparent        electrode 8 is connected to the other end of the second gate 22;    -   a flat isolation layer 9, located on the protective layer 7 and        the transparent electrode 8;    -   a pixel electrode 10, located on the flat isolation layer 9, and        the pixel electrode 10 is connected to the second source/the        second drain 62 and overlaps with the transparent electrode 8;    -   a pixel definition layer 11, located on the flat isolation layer        9 and the pixel electrode 10, and the pixel definition layer 11        comprises an open corresponding to an overlapping district of        the pixel electrode 10 and the transparent electrode 8;    -   and a photoresist spacer 12 located on the pixel definition        layer 11.

The first gate 21, the first source/the first drain 61, and the etchingstopper layer 5, the first semiconductor layer 41, the gate isolationlayer 3 sandwiched in-between construct a first thin film transistorTFT1; the second gate 22, the second source/the second drain 62, and theetching stopper layer 5, the second semiconductor layer 42, the gateisolation layer 3 sandwiched in between construct a second thin filmtransistor TFT2; the transparent electrode 8, the pixel electrode 10 andthe flat isolation layer 9 sandwiched in-between construct a transparentcapacitor C.

Specifically, the first semiconductor layer 41 is an Indium Gallium ZincOxide (IGZO) semiconductor layer, and the second semiconductor layer 42is an IGZO semiconductor layer.

The transparent electrode 8 is an Indium Tin Oxide (ITO) transparentelectrode or an Indium Zinc Oxide (IZO) transparent electrode and thetransparent electrode 8 can be manufactured to have various shapes; thepixel electrode 10 is an ITO pixel electrode or an IZO pixel electrode.

Both the transparent electrode 8, the pixel electrode 10 are transparentwhich the light can pass through. The transparent capacitor C constructsthe activation area part of the pixel structure and is capable ofincreasing the activation area of the pixel and raising the apertureratio to increase the display brightness and reduce the powerconsumption.

Significantly, the transparent capacitor C is fully capable of replacingthe opaque capacitors constructed by two metal electrodes according toprior art, or partially replacing the opaque capacitors, which eithercan increase the activation area of the pixels and raising the apertureratio.

Please refer to FIG. 4, which is the second embodiment of the pixelstructure having high aperture according to the present invention. Thedifferences of the second embodiment from the first embodiment is thatthe pixel structure having high aperture ratio further comprises a firsttop gate electrode 81 right over the first gate 21 and between theprotective layer 7 and the flat isolation layer 9, and a second top gateelectrode 82 right over the second gate 22 and between the protectivelayer 7 and the flat isolation layer 9. Correspondingly, both the firstthin film transistor TFT1 and the second thin film transistor TFT2comprises a double gate structure. For making the most of themanufacture process and raising the production efficiency, the first,and the second top gate electrodes 81, 82 and the transparent electrode8 are formed in the same manufacture process at the same time. Thematerial of the first, and the second top gate electrodes 81, 82 and thematerial of the transparent electrode 8 are the same, which is ITO orIZO. Others are figured to be the same as the first embodiment. Therepeated description is omitted here.

The present invention further provides a circuit of pixel structurehaving high aperture ratio. FIG. 5 shows the first embodiment of thecircuit, comprising a first thin film transistor TFT1, a second thinfilm transistor TFT2, a transparent capacitor C, and a light emittingdiode D, and both two electrodes constructing the transparent capacitorC are transparent electrodes.

A gate of the first thin film transistor TFT1 is coupled to a gate drivevoltage signal V_(gate), and a source thereof is coupled to a data drivevoltage signal V_(data), and a drain thereof and a gate of the secondthin film transistor TFT2 are coupled; a source of the second thin filmtransistor TFT2 is coupled to a drive voltage signal V_(dd), and a drainthereof is coupled to an anode of the organic light emitting diode D; acathode of the organic light emitting diode D is coupled to a groundsignal V_(ss); one electrode of the transparent capacitor C is coupledto the gate of the second thin film transistor TFT2, and the otherelectrode thereof is coupled to the source of the second thin filmtransistor TFT2.

The first thin film transistor TFT1 is employed as a signal switch thinfilm transistor, and the second thin film transistor TFT2 is employed asa drive thin film transistor. The working principle of the circuit is:when the gate drive voltage signal V_(gate) is present, the first thinfilm transistor TFT1 is conducted, and the data drive voltage signalV_(data) is inputted to the gate of the second thin film transistor TFT2and the second thin film transistor TFT2 is conducted. The drive voltagesignal V_(dd), drive the organic light emitting diode D to display afterbeing amplified by the second thin film transistor TFT2. When the gatedrive voltage signal V_(gate) disappears, the transparent capacitor C isemployed to maintain the voltage level of the pixel electrode.

The aperture ratio can be raised and the display effect can be promotedbecause the transparent electrode C is arranged in the circuit.

Please refer to FIG. 6, which is the second embodiment of the circuit ofthe pixel structure having high aperture according to the presentinvention. The differences of the second embodiment from the firstembodiment is that one electrode of the transparent electrode C iscoupled to the gate of the second thin film transistor TFT2, and theother electrode thereof is coupled to the drain of the second thin filmtransistor TFT2. Others are figured to be the same as the firstembodiment. The repeated description is omitted here.

Please refer to FIG. 7, which is the third embodiment of the circuit ofthe pixel structure having high aperture according to the presentinvention. The differences of the third embodiment from the firstembodiment is that one electrode of the transparent electrode C iscoupled to the gate of the second thin film transistor TFT2, and theother electrode thereof is coupled to the drain of the second thin filmtransistor TFT2, and added is an opaque capacitor C″, and one electrodeof the opaque capacitor C″ is coupled to the gate of the second thinfilm transistor TFT2, and the other electrode thereof is coupled to thesource of the second thin film transistor TFT2.

The source, the drain of the first thin film transistor TFT1 areswitchable, and the source, the drain of the second thin film transistorTFT2 are switchable, too. Therefore, in the third embodiment, the oneelectrode of the transparent electrode C can be coupled to the gate ofthe second thin film transistor TFT2, and the other electrode thereof iscoupled to the source of the second thin film transistor TFT2, and theone electrode of the opaque capacitor C″ can be coupled to the gate ofthe second thin film transistor TFT2, and the other electrode thereofcan be coupled to the drain of the second thin film transistor TFT2.Others are figured to be the same as the first embodiment. The repeateddescription is omitted here.

In conclusion, according to the pixel structure having high apertureratio of the present invention, by arranging the transparent capacitorconstructed by the transparent electrode and the pixel electrode, andthe transparent capacitor is employed as the activation area part forincreasing the activation area of the pixel and raising the apertureratio to increase the display brightness and reduce the powerconsumption. According to the circuit of the pixel structure having highaperture ratio provided by the present invention, the aperture ratio canbe raised and the display effect can be promoted by arranging thetransparent capacitor.

Above are only specific embodiments of the present invention, the scopeof the present invention is not limited to this, and to any persons whoare skilled in the art, change or replacement which is easily derivedshould be covered by the protected scope of the invention. Thus, theprotected scope of the invention should go by the subject claims.

What is claimed is:
 1. A pixel structure having high aperture ratio,comprising a substrate, a first gate and a second gate, located at oneside of the substrate; a gate isolation layer, located on the first, thesecond gates and the gate isolation layer, and the gate isolation layercompletely covers the first gate and the substrate, and exposes two endsof the second gate; a first semiconductor layer, located on the gateisolation layer and right over the first gate; a second semiconductorlayer, located on the gate isolation layer and right over the secondgate; an etching stopper layer, located on the first, the secondsemiconductor layer and the gate isolation layer; a first source/a firstdrain, located on the first semiconductor layer and the etching stopperlayer; a second source/a second drain, located on the secondsemiconductor layer and the etching stopper layer, and the firstsource/the first drain are connected to the first semiconductor layerand one end of the second gate, and the second source/the second drainare connected to the second semiconductor layer; a protective layer,located on the first source/the first drain, the second source/thesecond drain and the etching stopper layer; a transparent electrode,located on the protective layer and at the other side of the substrate,and the transparent electrode is connected to the other end of thesecond gate; a flat isolation layer, located on the protective layer andthe transparent electrode; a pixel electrode, located on the flatisolation layer, and the pixel electrode is connected to the secondsource/the second drain and overlaps with the transparent electrode; apixel definition layer, located on the flat isolation layer and thepixel electrode, and the pixel definition layer comprises an opencorresponding to an overlapping district of the pixel electrode and thetransparent electrode; the first gate, the first source/the first drain,and the etching stopper layer, the first semiconductor layer, the gateisolation layer sandwiched in-between construct a first thin filmtransistor; the second gate, the second source/the second drain, and theetching stopper layer, the second semiconductor layer, the gateisolation layer sandwiched in between construct a second thin filmtransistor; the transparent electrode, the pixel electrode and the flatisolation layer sandwiched in-between construct a transparent capacitor.2. The pixel structure having high aperture ratio according to claim 1,wherein the transparent capacitor constructs an activation area part ofthe pixel structure.
 3. The pixel structure having high aperture ratioaccording to claim 1, wherein the transparent electrode is an ITOtransparent electrode or an IZO transparent electrode, and the pixelelectrode is an ITO pixel electrode or an IZO pixel electrode.
 4. Thepixel structure having high aperture ratio according to claim 1, furthercomprising a photoresist spacer located on the pixel definition layer.5. The pixel structure having high aperture ratio according to claim 1,further comprising a first top gate electrode right over the first gateand between the protective layer and the flat isolation layer, and asecond top gate electrode right over the second gate and between theprotective layer and the flat isolation layer.
 6. The pixel structurehaving high aperture ratio according to claim 5, wherein the first, thesecond top gate electrodes and the transparent electrode are formed atthe same time.
 7. The pixel structure having high aperture ratioaccording to claim 1, wherein the first semiconductor layer is an IGZOsemiconductor layer, and the second semiconductor layer is an IGZOsemiconductor layer.
 8. A circuit of a pixel structure having highaperture ratio, comprising a first thin film transistor, a second thinfilm transistor, a transparent capacitor, and a light emitting diode,and both two electrodes constructing the transparent capacitor aretransparent electrodes; a gate of the first thin film transistor iscoupled to a gate drive voltage signal, and a source thereof is coupledto a data drive voltage signal, and a drain thereof and a gate of thesecond thin film transistor are coupled; a source of the second thinfilm transistor is coupled to a drive voltage signal, and a drainthereof is coupled to an anode of the organic light emitting diode; acathode of the organic light emitting diode is coupled to a groundsignal; one electrode of the transparent capacitor is coupled to thegate of the second thin film transistor, and the other electrode thereofis coupled to the source or the drain of the second thin filmtransistor.
 9. The circuit of the pixel structure having high apertureratio according to claim 8, further comprising an opaque capacitor, andone electrode of the opaque capacitor is coupled to the gate of thesecond thin film transistor, and the other electrode thereof is coupledto the source or the drain of the second thin film transistor.
 10. Thecircuit of the pixel structure having high aperture ratio according toclaim 9, wherein the source, the drain of the first thin film transistorare switchable, and the source, the drain of the second thin filmtransistor are switchable, too.
 11. A circuit of a pixel structurehaving high aperture ratio, comprising a first thin film transistor, asecond thin film transistor, a transparent capacitor, and a lightemitting diode, and both two electrodes constructing the transparentcapacitor are transparent electrodes; a gate of the first thin filmtransistor is coupled to a gate drive voltage signal, and a sourcethereof is coupled to a data drive voltage signal, and a drain thereofand a gate of the second thin film transistor are coupled; a source ofthe second thin film transistor is coupled to a drive voltage signal,and a drain thereof is coupled to an anode of the organic light emittingdiode; a cathode of the organic light emitting diode is coupled to aground signal; one electrode of the transparent capacitor is coupled tothe gate of the second thin film transistor, and the other electrodethereof is coupled to the source or the drain of the second thin filmtransistor; the circuit of the pixel structure having high apertureratio further comprises an opaque capacitor, and one electrode of theopaque capacitor is coupled to the gate of the second thin filmtransistor, and the other electrode thereof is coupled to the source orthe drain of the second thin film transistor; wherein the source, thedrain of the first thin film transistor are switchable, and the source,the drain of the second thin film transistor are switchable, too.